This invention relates generally to new toner compositions, and more specifically, to single component magnetic toners, wherein the magnetic component is treated with organic coupling materials, thereby, in one embodiment, reducing the fusing energy of the resulting toner.
In the electrophotographic process, especially the xerographic process, and in magnetic imaging systems similar steps are involved in causing the formation and development of images, including for example the formation of a latent image, the development of the latent image with a developing composition containing toner, optionally transferring the developed image to a suitable support such as paper, fusing the image to the paper substrate using a number of known techniques, including those employing heat, and optionally cleaning the surface from which the developed latent image has been transferred. In the xerographic process, the photoconductive surface or plate which contains an electrostatic latent image can be developed by means of a variety of pigmented resin materials specifically made for this purpose, such as toners. The toner material is electrostatically attracted to the latent image on the plate in proportion to the charge concentration thereon. These toner materials can be applied by a number of known techniques including for example, cascade development, see U.S. Pat. No. 3,618,552, magnetic brush development, see U.S. Pat. No. 2,874,063, and touchdown development, see U.S. Pat. No. 3,166,432. The developed image is then transferred to a suitable substrate such as paper, and can be fixed by using a number of different techniques including for example vapor fixing, heat fixing, pressure fixing or combinations thereof as described for example in U.S. Pat. No. 3,539,161.
In magnetic imaging systems substantially the same process steps are involved as described above with respect to electrophotographic imaging systems, thus there is formed a latent magnetic image on a magnetizable recording medium, which image can be used in duplicating processes, for example, by repetitive toning and transfer of the developed image. The latent magnetic image is formed by any suitable magnetization procedure whereby a magnetized layer of marking material is magnetized, and such magnetism transferred imagewise to the magnetic substrate; or where the magnetization pattern is applied directly to the magnetic substrate by a record head, or similar device. The latent magnetic image can be developed with a magnetic developer usually toner with a magnetic pigment to render such image visible. The developed visible magnetic image can then be typically transferred to a receiver such as for example a sheet of paper, which image is fused on the paper in order to produce a final copy or print referred to in the art as a hard copy.
One method of developing magnetic images is referred to as magnetic toner touchdown development, which involves providing a substantially uniform layer of toner comprising magnetic material on a conductive substrate, which material can be brought either closely adjacent to that of the image or in contact with the image. The magnetic material in the toner acts as an extension of the conductive backing and therefore acquires charge, induced therein by the latent image of a polarity opposite to that of the latent image. The conductive substrate can be biased to assist in transfer of the toner to the latent image, however, a conductive backing is not essential.
Typical suitable fusing methods that may be used have been described in the prior art and include for example, heating the toner and the developed image to cause the resins thereof to at least partially melt, and become adhered to the photoconductor binder member, or copy substrate, in the case of images transferred from the imaging media followed by the application of pressure to the toner with heating such as the use of a heated roller. Solvent or solvent vapor fusing has also been used, wherein the resin component of the toner is partially dissolved. The photoconductor binder member or copy substrate is typically of sufficient hardness to allow fixing solely by the application of pressure such as for example by a contact roller and in an amount sufficient to calender the toner.
Interest in magnetic toners, and more specifically, single development toners, that is, toners that do not contain carrier materials has increased rather significantly over the past several years. However, in many instances, such toners, particularly those containing certain magnetic pigments, possess a high fusing temperature thereby adversely affecting the imaging material over a period of time. Reducing the fusing temperature of the toner will result in a reduction in the amount of energy that is required to fuse the toner to the substrate such as paper, and thus allow the production of better quality images over longer periods of time.